How well do the disks play on your computer? If you don’t have software for playing dvd-video, try VLC media player, which is free to download and use: www.videolan.org Find out if your dvd drive in your computer is better at reading them.
The first thing I would try, assuming these disks are not encrypted, would be simply to go to the dvd drive in My Computer, right click on it and copy and paste the contents of the disk to the hard drive. Worth a shot anyway. 
Using dvd copying programs that have been developed for commercially made movies might be problematic. Most will shut down after failing to copy after a few times. Some can be set up to ignore read errors, but the result may not be useful. If you want to try this, you can get DVDDecrypter from www.mrbass.org To get it to ignore read errors, look in Tools–>Settings–>I/O tab, and put a check mark in the Ignore Read Errors box.
A better tool might be ISOBuster. There is a free version available for download, but the actions you need to copy might be more than the free one can do. You might be prompted to buy the full version. And if the disks are encrypted, this program will not work.
ISOPuzzle is freeware but I have not used it.
